MN
Matthew S. Nelson
  • BioTechnology Institute, University of Minnesota, USA
Research fields
  • Microbiology
Quantitative Evaluation of Competitive Nodulation among Different Sinorhizobium Strains
Authors:  Chan Lan Chun, Matthew S. Nelson and Michael J. Sadowksy, date: 08/05/2015, view: 7076, Q&A: 0
Legumes play a vital role in global food supply because they are uniquely capable of fixing atmospheric nitrogen (N) through symbioses with root and stem nodule bacteria, collectively called the rhizobia. These commonly include bacteria in the genera Rhizobium, Mesorhizobium, Sinorhizobium (Ensifer), and Bradyrhizobium, although other genera of bacteria have now been shown to form root nodule symbioses with several legume species (Weir, 2012). The symbiotic interaction is important for agricultural productivity, especially in less developed countries where nitrogen fertilizer is expensive. However, nodulation ability and competitiveness have practical importance in agricultural production, because the inoculation of efficient rhizobia is often unsuccessful, due to large part to the presence of competitive populations of ineffective indigenous rhizobia in soils (Toro, 1996; Triplett and Sadowsky, 1992). This protocol allows one us to quantitatively evaluate the relative nodulation competitiveness of Sinorhizobium strains.
Evaluation of Nodulation Speed by Sinorhizobium Strains
Authors:  Matthew S. Nelson, Chan Lan Chun and Michael J. Sadowksy, date: 08/05/2015, view: 8732, Q&A: 0
Rhizobia interact symbiotically with legumes to form root nodules, where by rhizobia fix atmospheric dinitrogen into ammonia in exchange for carbon produced via photosynthesis. The symbiotic interaction is agriculturally important by reducing the need for fertilizer containing nitrogen. The root and stem nodule bacteria commonly include bacteria in the genera Rhizobium, Mesorhizobium, Sinorhizobium (Ensifer), and Bradyrhizobium, although other genera of bacteria have now been shown to form root nodule symbioses with several legume species (Weir, 2012). Different rhizobial strains form different numbers of nodules on specific legume plant varieties (or cultivars), and the nitrogen fixing effectiveness of each rhizobial strain, its ability to fix nitrogen and transfer it to the plant, is also highly variable (Toro, 1996). Some native rhizobia are ineffective at fixing nitrogen yet form a majority of nodules in filed grown plants. This is referred to as the competition for nodulation problem (Triplett and Sadowsky, 1992). Competition studies are not feasible when evaluating a large number of different native strains. However, nodulation speed of individual strains correlates well with overall competiveness and can be used to identify native strains that overcome the competition problem (De Oliveira and Graham, 1990; Bhuvaneswari et al., 1980).
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